1. Field of the Invention
The present invention relates to 4xe2x80x2-C-ethynyl nucleosides and the use thereof for producing pharmaceuticals, and more particularly to the use thereof in treating acquired immunodeficiency syndrome (AIDS).
2. Background Art
The clinical setting for AIDS has been dramatically changed by a multi-drug therapy called highly active antiretroviral therapy, or HAART. In this therapy, nucleoside reverse transcriptase inhibitors (NRTIs) such as zidovudine (AZT), didanosine (ddI), zalcitabine (ddC), stavudine (d4T), and lamivudine (3TC) and protease inhibitors (PIs) are employed in combination. Application of this therapy has drastically decreased the number of deaths due to AIDS in many countries (Textbook of AIDS Medicine, p751 (Williams and Wilkins, Baltimore, 1999)).
In spite of the decrease in AIDS-related deaths due to HAART, there has emerged a multi-drug resistant HIV-1 (human immunodeficiency virus-1) mutant exhibiting cross-resistance to various drugs. For example, in the early 1990s patients infected with an HIV exhibiting resistance to both AZT and 3TC were very rare, whereas the percentage of AIDS patients infected with such an HIV was as high as 42% in 1995-1996 (AIDS, 11, 1184(1997)).
It has been reported that such multi-drug resistant viruses cause 30-60% of drug failure cases in which the viremia level drops once below the detection limit and then revives to exhibit lasting viremia (AIDS, 12, 1631(1998)). Thus, the present status of AIDS treatment is serious.
Conventionally, in terms of a compound which exhibits potent antiviral activities against multi-drug resistant viruses, there have been known only a few protease inhibitors; e.g., JE-2147, which have potent antiviral activity against a multi-PI resistant HIV-1 (Proc. Natl. Acad. Sci. USA, 96,8675(1999)). However, no nucleoside derivative having such potent activities has been reported yet.
Ohrui, one of the inventors of the present invention, has synthesized 1-(4-C-ethynyl-xcex2-D-ribo-pentofuranosyl)thymine, 4xe2x80x2-C-ethynyluridine, and 4xe2x80x2-C-ethynylcytidine and assayed biological activities such as antiviral and antitumor activities thereof. However, no such biological activities have been observed for these compounds (Biosci. Biotechnol. Biochem., 63(4), 736-742, 1999).
Furthermore, Matsuda et al. have synthesized 4xe2x80x2-C-ethynylthymidine and assayed the anti-HIV activity thereof. The anti-HIV activity of the compound is weaker than that of AZT. However, the assay described by Matsuda et al. (Bioorg. Med. Chem. Lett., 9(1999), 385-388) is drawn to an ordinary assay for determining anti-HIV activity on the basis of MT-4 cells versus an HIV-1 IIIb strain, and does not use a multi-drug resistant virus strain.
In order to find a compound having more potent antiviral activity than AZT, the present inventors have synthesized a variety of 4xe2x80x2-C-ethynyl nucleosides and evaluated the antiviral activity thereof, and have found that: 1) a 4xe2x80x2-ethynyl nucleoside derviative having a specific structure exhibits potent anti-HIV activity equal to or greater than that of AZT; 2) the compound has potent antiviral activity against a multi-drug resistant virus strain exhibiting resistance to various anti-HIV drugs such as AZT, ddI, ddC, d4T, and 3TC; and 3) the compound exhibits no significant cytotoxicity. The present invention has been accomplished on the basis of these findings.
Accordingly, the present invention provides 4xe2x80x2-C-ethynyl nucleosides (other than 4xe2x80x2-C-ethynylthymidine) represented by formula [I]: 
wherein B represents a base selected from the group consisting of pyrimidine, purine, and derivatives thereof; X represents a hydrogen atom or a hydroxyl group; and R represents a hydrogen atom or a phosphate residue.
The present invention also provides a pharmaceutical composition containing any one of the compounds and a pharmaceutically acceptable carrier.
Preferably, the composition is employed as an antiviral drug or a drug for treating AIDS. 
The present invention also provides use, as pharmaceuticals, of compounds represented by formula [1].
The present invention also provides a method for treatment of AIDS, comprising administering a compound of formula [1] to a vertebrate, including human.
The compounds of the present invention are represented by formula [I]. Examples of bases in formula [I] represented by B include pyrimidines; purines, including azapurines and deazapurines; and derivatives thereof.
Examples of substituents in the bases includes a halogen atom, an alkyl group, a haloalkyl group, an alkenyl group, a haloalkenyl group, an alkynyl group, an amino group, an alkylamino group, a hydroxyl group, a hydroxyamino group, an aminoxy group, an alkoxy group, a mercapto group, an alkylmercapto group, an aryl group, an aryloxy group, and a cyano group. The number and substitution site of these substituents are not particularly limited.
Examples of halogen atoms serving as substituents include chlorine, fluorine, iodine, and bromine. Examples of alkyl groups include C1-C7 alkyl group such as methyl, ethyl, and propyl. Examples of haloalkyl groups include C1-C7 haloalkyl groups such as fluoromethyl, difluoromethyl, trifluoromethyl, bromomethyl, and bromoethyl. Examples of alkenyl groups include C2-C7 alkenyl groups such as vinyl and allyl. Examples of haloalkenyl groups include C2-C7 haloalkenyl groups such as bromovinyl and chlorovinyl. Examples of alkynyl groups include C2-C7 alkynyl groups such as ethynyl and propynyl. Examples of alkylamino groups include C1-C7 alkylamino groups such as methylamino and ethylamino.
Examples of alkoxy groups include C1-C7 alkoxy groups such as methoxy and ethoxy. Examples of alkylmercapto groups include C1-C7 alkylmercapto groups such as methylmercapto and ethylmercapto. Examples of aryl groups include a phenyl group; alkylphenyl groups having a C1-C5 alkyl such as methylphenyl and ethylphenyl; alkoxyphenyl groups having a C1-C5 alkoxy such as methoxyphenyl and ethoxyphenyl; alkylaminophenyl groups having a C1-C5 alkyl such as dimethylaminophenyl and diethylaminophenyl; and halogenophenyl groups such as chlorophenyl and bromophenyl.
Examples of pyrimidine bases and derivatives thereof include cytosine, uracil, 5-fluorocytosine, 5-fluorouracil, 5-chlorocytosine, 5-chlorouracil, 5-bromocytosine, 5-bromouracil, 5-iodocytosine, 5-iodouracil, 5-methylcytosine, 5-ethylcytosine, 5-methyluracil (thymine), 5-ethyluracil, 5-fluoromethylcytosine, 5-fluorouracil, 5-trifluorocytosine, 5-trifluorouracil, 5-vinyluracil, 5-bromovinyluracil, 5-chlorovinyluracil, 5-ethynylcytosine, 5-ethynyluracil, 5-propynyluracil, pyrimidin-2-one, 4-hydroxyaminopyrimidin-2-one, 4-aminoxypyrimidin-2-one, 4-methoxypyrimidin-2-one, 4-acetoxypyrimidin-2-one, 4-fluoropyrimidin-2-one, and 5-fluoropyrimidin-2-one.
Examples of purine bases and derivatives thereof include purine, 6-aminopurine (adenine), 6-hydroxypurine, 6-fluoropurine, 6-chloropurine, 6-methylaminopurine, 6-dimethylaminopurine, 6-trifluoromethylaminopurine, 6-benzoylaminopurine, 6-acethylaminopurine, 6-hydroxyaminopurine, 6-aminoxypurine, 6-methoxypurine, 6-acetoxypurine, 6-benzoyloxypurine, 6-methylpurine, 6-ethylpurine, 6-trifluoromethylpurine, 6-phenylpurine, 6-mercaputopurine, 6-methylmercaputopurine, 6-aminopurine-1-oxide, 6-hydroxypurine-1-oxide, 2-amino-6-hydroxypurine(guanine), 2,6-diaminopurine, 2-amino-6-chloropurine, 2-amino-6-iodepurine, 2-aminopurine, 2-amino-6-mercaptopurine, 2-amino-6-methylmercaptopurine, 2-amino-6-hydroxyaminopurine, 2-amino-6-methoxypurine, 2-amino-6-benzoyloxypurine, 2-amino-6-acetoxypurine, 2-amino-6-methylpurine, 2-amino-6-cyclopropylaminomethylpurine, 2-amino-6-phenylpurine, 2-amino-8-bromopurine, 6-cyanopurine, 6-amino-2-chloropurine (2-chloroadenine), 6-amino-2-fluoropurine (2-fluoroadenine), 6-amino-3-deazapurine, 6-amino-8-azapurine, 2-amino-6-hydroxy-8-azapurine, 6-amino-7-deazapurine, 6-amino-1-deazapurine, and 6-amino-2-azapurine.
When B is a pyrimidine base and X is a hydrogen atom, examples of compounds represented by formula [I] include the following compounds:
4xe2x80x2-C-ethynyl-2xe2x80x2-deoxycytidine,
4xe2x80x2-C-ethynyl-2xe2x80x2-deoxy-5-halogenocytidine,
4xe2x80x2-C-ethynyl-2xe2x80x2-deoxy-5-alkylcytidine,
4xe2x80x2-C-ethynyl-2xe2x80x2-deoxy-5-haloalkylcytidine,
4xe2x80x2-C-ethynyl-2xe2x80x2-deoxy-5-alkenylcytidine,
4xe2x80x2-C-ethynyl-2xe2x80x2-deoxy-5-haloalkenylcytidine,
4xe2x80x2-C-ethynyl-2xe2x80x2-deoxy-5-alkynylcytidine,
4xe2x80x2-C-ethynyl-2xe2x80x2-deoxy-5-halogenouridine,
4xe2x80x2-C-ethynyl-2xe2x80x2-deoxy-5-alkyluridine (other than 4xe2x80x2-C-ethynylthymidine),
4xe2x80x2-C-ethynyl-2xe2x80x2-deoxy-5-haloalkyluridine,
4xe2x80x2-C-ethynyl-2xe2x80x2-deoxy-5-alkenyluridine,
4xe2x80x2-C-ethynyl-2xe2x80x2-deoxy-5-haloalkenyluridine, and
4xe2x80x2-C-ethynyl-2xe2x80x2-deoxy-5-alkynyluridine, and 5xe2x80x2-phoshate esters thereof.
When B is a pyrimidine base and X is a hydroxyl group, examples of compounds represented by formula [I] include the following compounds:
1-(4-C-ethynyl-xcex2-D-arabino-pentofuranosyl)cytosine,
1-(4-C-ethynyl-xcex2-D-arabino-pentofuranosyl)-5-halogenocytosine,
1-(4-C-ethynyl-xcex2-D-arabino-pentofuranosyl)-5-alkylcytosine,
1-(4-C-ethynyl-xcex2-D-arabino-pentofuranosyl)-5-haloalkylcytosine,
1-(4-C-ethynyl-xcex2-D-arabino-pentofuranosyl)-5-alkenylcytosine,
1-(4-C-ethynyl-xcex2-D-arabino-pentofuranosyl)-5-haloalkenylcytosine,
1-(4-C-ethynyl-xcex2-D-arabino-pentofuranosyl)-5-alkynylcytosine,
1-(4-C-ethynyl-xcex2-D-arabino-pentofuranosyl)-5-halogenouracil,
1-(4-C-ethynyl-xcex2-D-arabino-pentofuranosyl)-5-alkyluracil,
1-(4-C-ethynyl-xcex2-D-arabino-pentofuranosyl)-5-haloalkyluracil,
1-(4-C-ethynyl-xcex2-D-arabino-pentofuranosyl)-5-alkenyluracil,
1-(4-C-ethynyl-xcex2-D-arabino-pentofuranosyl)-5-haloalkenyluracil, and
1-(4-C-ethynyl-xcex2-D-arabino-pentofuranosyl)-5-alkynyluracil, and 5xe2x80x2-phoshate esters thereof.
When B is a purine base and X is a hydrogen atom, examples of compounds represented by formula [I] include the following compounds:
4xe2x80x2-C-ethynyl-2xe2x80x2-deoxyadenosine,
4xe2x80x2-C-ethynyl-2xe2x80x2-deoxyguanosine,
4xe2x80x2-C-ethynyl-2xe2x80x2-deoxyinosine,
9-(4-C-ethynyl-2-deoxy-xcex2-D-ribo-furanosyl)purine, and
9-(4-C-ethynyl-2-deoxy-xcex2-D-ribo-furanosyl)-2,6-diaminopurine, and 5xe2x80x2-phoshate esters thereof.
When B is a purine base and X is a hydroxyl group, examples of compounds represented by formula [I] include the following compounds:
9-(4-C-ethynyl-xcex2-D-arabino-pentofuranosyl)adenine,
9-(4-C-ethynyl-xcex2-D-arabino-pentofuranosyl)guanine,
9-(4-C-ethynyl-xcex2-D-arabino-pentofuranosyl)hypoxanthine,
9-(4-C-ethynyl-xcex2-D-arabino-pentofuranosyl)purine, and
9-(4-C-ethynyl-xcex2-D-arabino-pentofuranosyl)-2,6-diaminopurine, and 5xe2x80x2-phoshate esters thereof.
Examples of preferred compounds of the present invention includes the following compounds:
(i) 4xe2x80x2-C-ethynyl pyrimidine nucleosides including
(1) a compound represented by formula [I] wherein X is a hydrogen atom,
(2) a compound represented by formula [I] wherein X is a hydroxyl group,
(3) a compound represented by formula [I] wherein B is cytosine,
(4) a compound represented by formula [I] wherein B is cytosine and X is a hydrogen atom,
(5) a compound represented by formula [I] wherein B is cytosine and X is a hydroxyl group,
(6) 4xe2x80x2-C-ethynyl-2xe2x80x2-deoxycytidine,
(7) 4xe2x80x2-C-ethynyl-2xe2x80x2-deoxy-5-fluorocytidine, and
(8) 1-(4-C-ethynyl-xcex2-D-arabinofuranosyl)cytosine, and
(ii) 4xe2x80x2-C-ethynyl purine nucleosides including
(1) a compound represented by formula [I] wherein X is a hydrogen atom,
(2) a compound represented by formula [I] wherein X is a hydroxyl group,
(3) a compound represented by formula [I] wherein B is selected from the group consisting of adenine, guanine, hypoxanthine, and diaminopurine,
(4) a compound represented by formula [I] wherein B is selected from the group consisting of adenine, guanine, hypoxanthine, and diaminopurine and X is a hydrogen atom,
(5) a compound represented by formula [I] wherein B is selected from the group consisting of adenine, guanine, hypoxanthine, and diaminopurine and X is a hydroxyl group,
(6) 4xe2x80x2-C-ethynyl-2xe2x80x2-deoxyadenosine,
(7) 4xe2x80x2-C-ethynyl-2xe2x80x2-deoxyguanosine,
(8) 4xe2x80x2-C-ethynyl-2xe2x80x2-deoxyinosine,
(9) 9-(4-C-ethynyl-2-deoxy-xcex2-D-ribo-pentofuranosyl)-2,6-diaminopurine, and
(10) 9-(4-C-ethynyl-xcex2-D-arabino-pentofuranosyl)adenine.
The compounds of the present invention may be salts, hydrates, or solvates. When R is a hydrogen atom, examples of salts include acid-adducts such as hydrochlorides and sulfates. When R is a phosphate residue, examples of salts include alkali metal salts such as sodium salts, potassium salts, and lithium salts; alkaline earth metal salts such as calcium salts; and ammonium salts. These salts are pharmaceutically acceptable.
Examples of hydrates or solvates include adducts comprising one molecule of the compound of the present invention or a salt thereof and 0.1-3.0 molecules of water or a solvent. In addition, the compounds of the present invention encompass a variety of isomers thereof such as tautomers.
One of the compounds of the present invention in which X is a hydrogen atom; i.e., a 2xe2x80x2-deoxy derivative, can be produced by the following steps.
First Step;
In the first step, a hydroxymethyl group at the 4-position of the compound represented by [II] is oxidized to thereby form an aldehyde, which is further converted into an alkyne to thereby yield a compound represented by formula [III]: 
wherein each of R1 and R2 represents a protective group; R3 represents a hydrogen atom or a protective group; and Bn represents a benzyl group.
The starting material of the reaction is a known compound represented by formula [II] (Biosci. Biotech. Biochem., 57, 1433-1438(1993)).
Each of R1 and R2 may be a protective group which is typically employed for protecting a hydroxyl group. Examples of types of a protective moiety containing R1 or R2 include an ether type, an acyl type, a silyl type, and an acetal type. Specific examples protective groups include a silyl group, an acetyl group, a benzyl group, and an isopropylidenyl group.
When the hydroxymethyl group at the 4-position of the compound represented by [II] is converted into an aldehyde group by use of an oxidizing agent, examples of oxidizing agents include a chromium-containing oxidizing agent such as chromic anhydride-pyridine-acetic anhydride composite reagent, pyridinium chlorochromate, or pyridinium dichromate; a high-valency iodine oxidizing agent such as Dess-Martin reagent; and a dimethylsulfoxide-based oxidizing agent such as a combination of dimethylsulfoxide and any one of acetic anhydride, oxalyl chloride, or dicyclohexyl carbodiimide.
Reaction conditions vary depending on an employed oxidizing agent. For example, when oxidation is carried out by use of oxalyl chloride and dimethyl sulfoxide, oxaly chloride in an amount of 0.5-5 mol and dimethyl sulfoxide in an amount of 1.5-6 mol are added to 1 mol of a compound represented by formula [II] in an organic solvent such as dichloromethane optionally under an inert gas such as argon or nitrogen. The mixture is then allowed to react for approximately 15 minutes to two hours at xe2x88x92100xc2x0 C. to 0xc2x0 C. Subsequently, a base such as triethylamine is added in an amount of 2-10 mol to the mixture, and the resultant mixture is further allowed to react at room temperature for approximately 15 minutes to two hours.
The thus-formed aldehyde can be converted into a corresponding alkyne through carbon-increasing (i.e., Cxe2x80x94C bond formation) reaction of the aldehyde; treating the resultant compound with a strong base to thereby form a metal alkynyl compound; and introducing a protective group to the metal alkynyl compound.
Carbon-increasing reaction may be carried out in an organic solvent such as dichloromethane or dichloroethane, optionally under an inert gas such as argon or nitrogen. Specifically, 1 mol of the above-produced aldehyde is reacted with 1-5 mol of carbon tetrabromide and 2-10 mol of triphenylphosphine at 0-50xc2x0 C. for approximately 15 minutes to three hours.
Treatment with a strong base may be carried out in an organic solvent such as tetrahydrofuran, 1,4-dioxane, or dimethoxyethane, optionally under an inert gas such as argon or nitrogen. Specifically, 1 mol of a compound obtained through carbon-increasing reaction is reacted with 2-4 mol of a lithium compound such as n-butyllithium or t-butyllithium at xe2x88x92100xc2x0 C. to xe2x88x9220xc2x0 C. for approximately 5-60 minutes.
Furthermore, when a silyl protective group represented by R3 is introduced into an alkynyl group in the thus-obtained compound, the aforementioned treatment is followed by addition of a silylating agent such as chlorotriethylsilane. A protective group can be introduced to a hydroxyl group by use of a customary method. For example, an acetyl group may be introduced through reaction with an acetylating agent such as acetic anhydride.
The thus-obtained compound represented by formula [III] may be isolated and purified through a manner which is employed for isolating and purifying typical protected saccharides. For example, the crude compound is partitioned by use of an ethyl acetate-saturated sodium bicarbonate solution, and the isolated compound is purified by use of a silica gel column.
Second step;
The second step includes condensation of a compound represented by formula [III] and a base represented by B; deoxygenation at the 2xe2x80x2-position; removing a protective group of a saccharide portion; and optionally phosphorylating the hydroxyl group at the 5xe2x80x2-position, to thereby produce a compound represented by formula [I]: 
wherein B represents a base selected from the group consisting of pyrimidine; purine, including azapurine or deazapurine; and a derivative thereof (other than thymine); R represents a hydrogen atom or a phosphate residue; each of R1 and R2 represents a protective group; R3 represents a hydrogen atom or a protective group; and Bn represents a benzyl group.
Condensation of a compound represented by formula [III] and a base represented by B can be carried out by reacting the compound with the base in the presence of a Lewis acid.
The base represented by B may be silylated, and silylation may be carried out through a known method. For example, a base is silylated by use of hexamethylsilazane and trimethylchlorosilane under reflux.
Examples of Lewis acids include trimethylsilyl trifluoromethanesulfonate, tin tetrachloride, zinc chloride, zinc iodide, and anhydrous aluminum chloride.
Condensation reaction may be carried out in an organic solvent such as dichloromethane, 1,2-dichloroethane, acetonitrile, or toluene, optionally under an inert gas such as argon or nitrogen. Specifically, 1 mol of a compound represented by formula [III] is reacted with 1-10 mol of a base represented by B and 0.1-10 mol of Lewis acid at xe2x88x9220xc2x0 C. to 150xc2x0 C. for approximately 30 minutes to three hours.
Deoxygenation at the 2xe2x80x2-position may be carried out by converting the derivative having a hydroxyl group to the derivative having a group such as halogeno, phenoxythiocarbonyl, thiocarbonylimidazolyl, or methyldithiocarbonyl and reducing the converted derivative using a radical reducing agent in the presence of a radical initiator.
For example, when deoxygenation is carried out through phenoxythiocarbonate, conversion of a hydroxyl group to a phenoxythiocarbonyl group may be carried out in an organic solvent, such as tetrahydrofuran, acetonitrile, or dichloromethane, in the presence of a base such as dimethylaminopyridine or pyridine, optionally under an inert gas such as argon or nitrogen. Specifically, 1 mol of the aforementioned condensation product in which only the protective group for the hydroxyl group at the 2xe2x80x2-position had been eliminated is reacted under stirring with 1-10 mol, preferably 1.1-2 mol, of a phenyl chlorothionoformate derivative at 0-50xc2x0 C. for approximately 0.5-5 hours. Alternatively, when deoxygenation is carried out via a bromo compound, the bromination may be carried out in an organic solvent, such as tetrahydrofuran, acetonitrile, or dichloromethane, by use of a brominating agent such as acetyl bromide at 0-150xc2x0 C. for approximately 0.5-5 hours, optionally under an inert gas such as argon or nitrogen. The brominating agent is used in an amount of 1-50 mol, preferably 5-20 mol, per mol of the aforementioned condensate from which a protective group at the 2xe2x80x2-position had been removed.
Subsequently, reduction may be carried out in an organic solvent such as toluene or benzene in the presence of a radical initiator such as azobisisobutyronitrile, optionally under an inert gas such as argon or nitrogen. Specifically, 1 mol of the aforementioned phenoxythiocarbonate or bromide is reacted under stirring with 1-10 mol, preferably 2-5 mol, of a radical reducing agent such as tributyltin hydride at 50-150xc2x0 C. for approximately 1-5 hours.
One of the compounds of the present invention in which X is a hydroxyl group; i.e., an arabino derivative, can be produced by the following steps.
First step;
The first step includes condensation of a compound represented by formula [III] and a base represented by B; stereochemically inverting the hydroxyl group at the 2xe2x80x2-position to be an arabino form; removing a protective group of a saccharide portion; and optionally phosphorylating the hydroxyl group at the 5xe2x80x2-position, to thereby produce a compound represented by formula [I]: 
wherein B represents a base selected from the group consisting of pyrimidine, purine including azapurine or deazapurine, and a derivative thereof; R represents a hydrogen atom or a phosphate residue; each of R1 and R2 represents a protective group; R3 represents a hydrogen atom or a protective group; and Bn represents a benzyl group.
Condensation of a compound represented by formula [III] and a base represented by B can be carried out by reacting the compound with the base in the presence of a Lewis acid.
The base represented by B may be silylated, and silylation may be carried out through a known method. For example, a base is silylated by use of hexamethylsilazane and trimethylchlorosilane under reflux.
Examples of Lewis acids include trimethylsilyl trifluoromethanesulfonate, tin tetrachloride, zinc chloride, zinc iodide, and anhydrous aluminum chloride.
Condensation reaction may be carried out in an organic solvent such as dichloromethane, 1,2-dichloroethane, acetonitrile, or toluene, optionally under an inert gas such as argon or nitrogen. Specifically, 1 mol of a compound represented by formula [III] is reacted with 1-10 mol of a base represented by B and 0.1-10 mol of Lewis acid at xe2x88x9220xc2x0 C. to 150xc2x0 C. for approximately 30 minutes to three hours.
Stereo-inversion of the hydroxyl group at the 2xe2x80x2-position can be carried out by converting a compound containing the hydroxyl into a corresponding 2,2xe2x80x2-anhydrocyclonucleoside and hydrolyzing the nucleoside. Anhydrocyclization may be carried out through treatment with a sulfonating agent such as methanesulfonyl chloride, or through treatment with a fluorinating agent such as diethylaminosulfur trifluoride.
For example, when diethylaminosulfur trifluoride is employed, anhydrocyclization may be carried out in an organic solvent such as dichloromethane or toluene, optionally under an inert gas such as argon or nitrogen. Specifically, 1 mol of the aforementioned condensation product in which the protective group for the hydroxyl group at the 2xe2x80x2-position was removed is reacted with 1.1-5 mol, preferably 1.5-2 mol, of diethylaminosulfur trifluoride at 0xc2x0 C. to room temperature for approximately five minutes to 2 hours. Alternatively, when methanesulfonyl chloride is employed, anhydrocyclization may be carried out in an organic solvent such as pyridine, optionally under an inert gas such as nitrogen. Specifically, 1 mol of the aforementioned condensation product in which the protective group for the hydroxyl group at the 2xe2x80x2-position had been eliminated is reacted with 1.1-5 mol, preferably 1.5-2 mol, of methanesulfonyl chloride at 0-50xc2x0 C. for approximately five minutes to 10 hours.
Subsequently, hydrolysis may be carried out in the presence of an appropriate base or acid catalyst. For example, when a base catalyst is employed, hydrolysis may be carried out in a solvent mixture comprising water and an alcoholic solvent such as ethanol in the presence of a base such as sodium hydroxide or potassium hydroxide at room temperature to 100xc2x0 C. for approximately 30 minutes to 5 hours.
In the case in which a base represented by B in the target compound; i.e., 4xe2x80x2-ethynylnucleoside, is a base having an amino group, the target compound may also be produced from a hydroxyl-containing base compound through a known method. Four example, if the 4-position of a pyrimidine base is sought to be aminated, the hydroxyl group at the 4-position of a pyrimidine base may be converted into a group such as chloro, silyloxy, alkyloxy, sulfonyloxy, or triazolyl, and then the converted group is reacted with ammonia. For example, amination through a triazole derivative may be carried out with stirring in an organic solvent such as dichloromethane, acetonitrile, dimethylformamide, or pyridine in the presence of a base such as triethylamine (triethylamine may be omitted if pyridine is used as a solvent) and a phosphorylating agent such as 4-chlorophenylphosphorodichloridate, optionally under an inert gas such as argon or nitrogen. Specifically, 1 mol of the aforementioned condensation product is reacted with 1-20 mol, preferably 2-10 mol, of 1,2,4-triazole at 0xc2x0 C. to room temperature for approximately 12-72 hours, followed by addition of aqueous ammonia in an appropriate amount and further reaction at 0xc2x0 C. to room temperature for approximately 1-12 hours.
In addition, an amino group in a base may be removed through a conventional method making use of any of a variety of deaminases, such as adenosine deaminase or cytidine deaminase.
Finally, a protective group of the thus-produced nucleoside is removed, to thereby obtain the compounds (R=H) of the present invention.
A protective group may be removed through a method appropriately selected from a routine procedure such as hydrolysis under acidic conditions, hydrolysis under basic conditions, treatment with tetrabutylammonium fluoride, or catalytic reduction, in accordance with the protective group employed.
When R in a target compound is a phosphate residue such as monophosphate or diphosphate, a compound in which R is a hydrogen atom is reacted with a phosphorylating agent; e.g., phosphorus oxychloride or tetrachloropyrophosphoric acid, which selectively phosphorylates the 5xe2x80x2-position of a nucleoside, to thereby produce a target compound in a free or salt form.
The compounds of the present invention may be isolated and purified through conventional methods, in appropriate combination, which are employed for isolating and purifying nucleosides and nucleotides; e.g., recrystallization, ion-exchange column chromatography, and adsorption column chromatography. The thus-obtained compounds may further be converted to a salt thereof in accordance with needs.
As shown in the below-described Test Examples, the compounds of the present invention exhibit excellent antiviral activity against herpesvirus or retrovirus. Thus, the compositions of the present invention containing one of the compounds of the present invention as an active ingredient can be used as therapeutic drugs. Specifically, the compositions of the present invention are useful for the treatment of infectious diseases caused by herpesvirus or retrovirus, in particular, AIDS, which is caused by HIV infection.
Examples of target viruses include viruses belonging to Herpesviridae such as herpes simplex virus type 1, herpes simplex virus type 2, or varicella-zoster virus, and Retroviridae such as human immunodeficiency virus.
The dose of the compounds of the present invention depends on and is determined in consideration of conditions such as the age, body weight, and type of disease of the patient; the severity of a disease of the patient; the drug tolerance; and the administration route. However, the dose per day and per body weight is selected typically within 0.00001-1,000 mg/kg, preferably 0.0001-100 mg/kg. The compounds are administered in a single or divided manner.
Any administration route may be employed, and the compounds may be administered orally, parenterally, enterally, or topically.
When a pharmaceutical is prepared from the compounds of the present invention, the compounds are typically mixed with customarily employed additives, such as a carrier and an excipient. Examples of solid carriers include lactose, kaolin, sucrose, crystalline cellulose, corn starch, talc, agar, pectin, stearic acid, magnesium stearate, lecitin, and sodium chloride. Examples of liquid carriers include glycerin, peanut oil, polyvinylpyrrolidone, olive oil, ethanol, benzyl alcohol, propylene glycol, and water.
The dosage form is arbitrarily selected. When the carrier is solid, examples of dosage forms include tablets, powder, granules, capsules, suppositories, and troches, whereas when it is liquid, examples include syrup, emulsion, soft-gelatin-encapsulated, cream, gel, paste, spray, and injection.
As shown in the below-described results of Test Examples, the compounds of the present invention exhibit excellent anti-HIV activity, particularly against multi-drug resistant HIV strains having resistance to various of anti-HIV drugs such as AZT, DDI, DDC, D4T, and 3TC. The compounds have no significant cytotoxicity. Thus, the compounds of the present invention are expected to be developed for producing pharmaceuticals, particularly drugs for treating AIDS.